Dinosaurs can be divided into plant-eaters or meat-eaters, although some may have been omnivores: they ate both animals and plants. The shape of a dinosaur’s jaws or teeth is often the first clue that reveals to which group it belonged and how it obtained its food. We know from the fossil record what food was available at a certain time. In some fossils, the stomach contents have also been preserved, providing vital clues about diet. We can also work out how dinosaurs fed simply by studying modern animals’ eating habits.

Gastroliths

The sauropods’ sheer size meant they would have needed immense amounts of food in the form of plant matter to nourish them. Yet their teeth were small, few in number and incapable of chewing. How could they digest their colossal meals?
The presence of pebbles in some fossil remains provides the answer. Known as gastroliths, these polished, rounded pebbles were a vital part of the digestive system.

​​​​​​​

Plant-eaters

Hadrosaurs, such as Saurolophus, had flat beaks and hundreds of cheek teeth. Using their beaks, hadrosaurs tore vegetation from trees, shrubs or other plants. They then either stored it in their cheeks for later consumption, or chewed it up in their teeth (the way their jaws were hinged enabled them to do this) before swallowing it.
​​​​​​​

Meat-eaters

For meat-eating dinosaurs, their food had to be found or caught. From the behaviour of modern lions and hyenas, we know that few large meat-eaters would turn down the opportunity to scavenge, or steal the kill of others. It is likely, however, that large theropods, with their powerful build, were primarily active hunters of other dinosaurs. We know from fossil evidence of stomach contents that some predators, especially smaller ones (much commoner in the fossil record than the giants) fed on smaller animals, such as fish, lizards, mammals and insects.

Fish-eaters

Fish scales have been found inside the fossil remains of Baryonyx. Its skull was long and narrow like a crocodile’s, with jaws lined with narrow, pointed and finely serrated teeth. So we know Baryonyx ate fish—but it is likely that it hunted other prey as well. No large land animals today can survive on a diet of fish alone. Iguanodon bones have also been found inside Baryonyx’s body cavity, suggesting that it could have scavenged on its corpse.